Catalytic composition and process for the transalkylation of aromatic hydrocarbons

ABSTRACT

Superior aromatic alkylation and transalkylation performance is obtained with a novel catalytic composition comprising a hydrogen form mordenite incorporated with alumina. The superior performance is a direct result of the catalyst composition having a surface area of at least 580 m 2  /g. A novel method of preparing a catalyst having a surface area of at least 580 m 2  /g is characterized by contacting a formed catalytic composite with an acidic aqueous solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of prior copendingapplication Ser. No. 124,147, filed Nov. 23, 1987, now U.S. Pat. No.4,826,801, which is a continuation-in-part of prior copendingapplication Ser. No. 932,113, filed Nov. 18, 1986, now U.S. Pat. No.4,735,929, which is a continuation-in-part of application Ser. No.772,099, filed Sept. 3, 1985, now abandoned, the contents of which areincorporated herein by reference thereto.

BACKGROUND OF THE INVENTION

The present invention is related to an improved catalytic compositionand an alkylation or transalkylation process employing that catalyticcomposition. More particularly, this invention involves an alkylation ortransalkylation catalyst composition comprising a hydrogen formcrystalline aluminosilicate zeolite and a refractory inorganic oxide.

The alkylation or transalkylation of aromatics are processes well knownfor their ability to produce such monoalkylaromatic products asethylbenzene, cumene, linear alkylbenzenes, and so forth. Suchmonoalkylaromatic compounds are important chemical precursors in theproduction of detergents and polymers among others. Alkylation catalyststhat are known to produce alkylaromatic compounds include the well-knownFriedel-Crafts catalysts: sulfuric acid, phosphoric acid, hydrofluoricacid, and aluminum chloride in either liquid or solid supported form.Solid granular catalysts such as clays, zeolites, and amorphousmaterials have also been utilized as alkylating reactants in both amodified and naturally occurring form.

A myriad of processing schemes employing an alkylation reaction zoneand/or a transalkylation reaction zone are well known to producemonoalkylaromatic products in high yields. One drawback concerningexisting alkylation/transalkylation processes is the potential for thealkylation and/or the transalkylation catalyst to produce undesirableproducts such as alkylating agent oligomers, heavy polyaromaticcompounds, and unwanted monoalkylaromatics. The alkylating agentoligomers can be especially troublesome as they are often recovered withthe desired monoalkylaromatic product where they can detrimentallyaffect the utility of the monoalkylaromatic product in furtherconversion processes. An example of this would be the contamination ofcumene with propylene oligomers which may reduce the utility of usingsuch contaminated cumene as a phenol process feedstock and ultimatelyfor the production of phenolic resins due to the presence of theoligomers as an inert compound within the cross-linked resins.

Another drawback inherent to some existing alkylation/transalkylationreaction zone containing processes is the use of Friedel-Craftscatalysts such as solid phosphoric acid or hydrofluoric acid as thealkylation and/or transalkylation catalysts. Many of these catalystsrequire a water cofeed and produce an extremely corrosive sludgeby-product. The utilization of such sludge-producing catalysts in analkylation process requires that special design considerations be maderegarding unit metallurgy, safety, and by-product neutralization. Suchdesign considerations are typically costly and may add significantly tothe construction and operations costs of such processes. Additionally,the use of Friedel-Crafts catalysts requires a once-through processingscheme to ensure that damaging corrosive materials are not recycled intothe reaction zone. This requirement necessitates the operation of theprocess at high conversion conditions which tend to produce greateramounts of unwanted by-products such as alkylating agent oligomers andheavy by-products.

More recently, crystalline aluminosilicate zeolites which have showncatalytic activity have been effectively used in the alkylation andtransalkylation of aromatics. Both natural and synthetic crystallinealuminosilicates have been employed. Included among these are the Type Xand Type Y zeolites as well as synthetic mordenite.

Specifically, the zeolites known as mordenites have received greatattention. Mordenites are crystalline natural or synthetic zeolites ofthe aluminosilicate type; generally, they have a composition expressedin moles of oxide of

    1.0±0.2 Na.sub.2 O•Al.sub.2 O.sub.3 •10±0.5 SiO.sub.2 ;

the quantity of SiO₂ may also be larger. Instead of all or part of thesodium, other alkali metals and/or alkaline earth metals may be present.

In general, it has been found that the sodium form of mordenite is notparticularly effective for the alkylation or transalkylation ofhydrocarbons and that replacing all, or for the greater part, of thesodium cations with hydrogen ions yields the more advantageous hydrogenform mordenite. Conversion of the sodium form to the hydrogen form canbe accomplished by a number of means. One method is the directreplacement of sodium ions with hydrogen ions using an acidified aqueoussolution where the process of ion exchange is employed. Another methodinvolves substitution of the sodium ions with ammonium ions followed bydecomposition of the ammonium form using a high temperature oxidativetreatment.

The activity and selectivity of alkylation or transalkylation catalystsdepend on a variety of factors, such as the mode of catalystpreparation, the presence or absence of promoters, quality of rawmaterials, feedstock quality, process conditions, and the like. Suitablecatalysts can be conventionally prepared by combining commerciallyavailable crystalline zeolites, such as, a hydrogen form mordenite, witha suitable matrix material. A new catalyst has now been discovered whichexhibits greatly improved alkylation and transalkylation performancewhen compared to conventionally prepared catalysts.

OBJECTS AND EMBODIMENTS

Accordingly, there is provided a catalyst composition for the alkylationand transalkylation of aromatic hydrocarbons, which comprises a hydrogenform mordenite, and from about 5 to 25 wt. % alumina. The support iscontacted with an acidic aqueous solution after it is formed. The acidiccontacting occurs at conditions selected to increase the surface area ofthe composite to at least 580 m² /g without increasing thesilica/alumina ration of the mordenite.

In another aspect, the invention is a method of manufacturing theaforementioned catalyst composition. Manufacturing of the catalystcomprises forming a composite comprising hydrogen form mordenite andfrom about 5 to 25 wt. % alumina, thereafter contacting formed compositewith an acidic aqueous solution under conditions selected to increasethe surface area of the composite to at least 580 m² /g withoutincreasing the silica/alumina ration of the mordenite.

In another aspect, the invention is process for alkylating ortransalkylating an aromatic hydrocarbon by contacting a feedstockcomprising an aromatic substrate and an alkylating agent or in the caseof transalkylation with a transalkylatable aromatic hydrocarbon in areaction zone with the catalyst composition described above.

These, as well as other embodiments of the present invention, willbecome evident from the following, more detailed description.

INFORMATION DISCLOSURE

The prior art recognizes a myriad of catalyst formulations for thealkylation or transalkylation of hydrocarbons. It is well known thatacids, such as strong mineral acids, can be used to modify crystallinealuminosilicate zeolite powders through decationization anddealumination. Ammonium compounds have also been successfully employedto convert crystalline aluminosilicates from alkali and/or alkalinemetal cation form to the hydrogen form. Combinations of zeolite andrefractory inorganic oxide have been disclosed, however, the art issilent as to the inherent problem of loss of the zeolite surface area asa result of dilution and forming techniques associated with therefractory inorganic oxide.

Combinations of the acid and ammonium treatments have been disclosed foruse on aluminosilicate powders. U.S. Pat. No. 3,475,345 (Benesi)discloses a method of converting aluminosilicate zeolites, particularlya sodium form synthetic mordenite, to the hydrogen form utilizing athree-step pretreatment performed on the powdered zeolite. Thesepretreatment steps consist of: (1) a hot acid treatment, (2) a cold acidtreatment, and (3) treatment with an ammonium compound. U.S. Pat. No.3,442,794 (Van Helden et al) also discloses a method for thepretreatment of aluminosilicate zeolites to the hydrogen form. Again,the preferred zeolite is the synthetic sodium form of mordenite. Themethod disclosed is very similar to U.S. Pat. No. 3,475,345 mentionedabove, with the distinguishing feature being a separately performedtwo-step pretreatment with (1) an acid compound and (2) an ammoniumcompound in arbitrary order. An important feature of both references isthat the treatments are performed solely on the aluminosilicate zeolitewith the express intention of modifying said zeolite before beingutilized in a catalyst formulation and that no mention of the importanceof the surface area of the catalytic composite is disclosed. This isdistinguished from the present invention in that any treatment performedis subsequent to the zeolite being incorporated into a formed catalystcomposite and more importantly without any apparent modification of thezeolite itself.

Treatment of the aluminosilicates with acid have not only been effectivefor conversion to the hydrogen form, but also have been used as a meansfor increasing the silica to alumina ratio. Typically, a silica toalumina ratio of about 10:1 is observed for a sodium for syntheticmordenite and is substantially unchanged if an ammonium treatment isused to convert the mordenite to the hydrogen form. If a mordenitepowder is subjected to an acid treatment as taught in U.S. Pat. No.3,597,155 (Flanigen), an increase in the silica to alumina ratio iseffected. The acid treatment is believed to cause a reduction of theframework tetrahedra aluminum atoms, thus increasing the proportion ofsilicon atoms present in the zeolitic structure.

Transalkylation performance is enhanced when the silica to alumina ratioof a mordenite powder is increased. U.S. Pat. No. 3,551,510 (Pollitzeret al) teaches the use of a hot hydrochloric acid extracted mordenitecatalyst in a transalkylation reaction zone. Again, this referencespecifically teaches of the use of acid treatment of the zeolite powderalone for the purpose of increasing the silica to alumina ratio, whereasthe subject invention incorporates an already high silica to aluminaratio crystalline aluminosilicate into the catalytic composite andpost-treats with acid to clean out the catalyst pores and therebyincrease the surface area of the catalyst. These references also do notteach the importance of the surface area of the catalytic composite orits relationship to aromatic alkylation or transalkylation performance.

A common attribute of the above-mentioned prior art is that, in allcases, the crystalline aluminosilicate alone, in particular thesynthetic sodium form of mordenite, is subjected to an acid and/or anammonium pretreatment step(s) to modify the aluminosilicate before itsincorporation into the catalyst composition. Although the pretreatmentof mordenite as described in the above references enhances theperformance of catalytic composites comprising such pretreatedmordenite, further improvements are still obtainable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the diisopropylbenzene (DIPB) conversion in percentexpressed alternatively as: ##EQU1## plotted against hours on-stream.

FIG. 2 is a plot of benzene conversion in percent plotted against hourson-stream where benzene conversion may be expressed as: ##EQU2##

DETAILED DESCRIPTION

While previous work dealt exclusively with pretreatment of thealuminosilicate component of a catalyst, it is one of the objects of thepresent invention to provide a novel catalyst composition which ischaracterized by exceptionally high surface area and which exhibitsimproved alkylation and transalkylation performance.

According to the present invention, there is provided a catalystcomposition for the alkylation or transalkylation of aromatichydrocarbons. The catalyst composition of the present inventioncomprises a hydrogen form mordenite and from about 0.5 to 50 wt. %alumina, and preferably 5 to 25 wt. % alumina with said catalystcomposition having a surface area of at least 580 m² /g. We have foundthat significant improvements in alkylation and transalkylationperformance are realized when the surface area of the catalystcomposition is at or above 580 m² /g. Although a maximum surface area ofthe catalyst composition has not been determined experimentally, it isbelieved that an upper limit of 700 m² /g is possible. Obtaining such ahigh surface area in the range from about 580 to 700 m² /g is the objectof one of the embodiments of the subject invention and is furtherillustrated in subsequent examples.

An essential component of the instant invention is the hydrogen formmordenite. While mordenite is naturally occurring, a variety ofsynthetic mordenites are available commercially, usually in a powderform. These synthetic mordenites can be obtained in both the sodium formand hydrogen form and at varied silica to alumina ratios. It is apreferred embodiment of the present invention that the mordenite be ofthe hydrogen form and that the silica to alumina ratio be at least 16:1,more specifically, in the range from 16:1 to 60:1. The pretreatmentsteps taught in the aforementioned references are routinely andtypically employed in the manufacture of commercially availablemordenite powders which meet the requirements as a starting material asset forth in the present invention. These pretreatment steps are used toincrease the silica to alumina ratio of the mordenite zeolite and toconvert the sodium form to the more desirable hydrogen form.

The hydrogen form mordenite is incorporated with alumina and formed intoa catalytic composite. The formed catalytic composite may be prepared byany known method in the art including the well-known oil drop andextrusion methods. The hydrogen form mordenite may be present in anamount within the range of 50 to about 99.5 wt. %, preferably within thecommercially desirable range of 75 to about 95 wt. %. Thus, the aluminais preferably present in an amount within the range of from about 5 toabout 25 wt. %, based on total weight of the catalyst composition.

The preferred alumina for use in the present invention is selected fromthe group consisting of gamma-alumina, eta-alumina, and mixturesthereof. Most preferred is gamma-alumina. Other refractory inorganicoxides which may be used include, for example, silica gel,silica-alumina, magnesia-alumina, zirconia alumina,phosphorus-containing alumina, and the like.

Surprisingly and unexpectedly, it has been found that a catalystcomposition prepared in accordance with and containing the components asclaimed in the invention will possess a surface area higher than anycatalyst heretofore described in the art. This high surface area of atleast 580 m² /g is surprising when one considers not only the dilutingaffect of an alumina support material having relatively low surface area(maximum approximately 250 m² /g), but also considering the lowering ofsurface area caused by the particular forming technique employed. Asexemplified herein below, catalyst of the prior art do not obtain thehigh surface area of the instant catalyst and thus demonstrate inferiorperformance, particularly as alkylation and transalkylation catalysts.The prior art does not teach or suggest how to obtain amordenite/alumina catalyst having a surface area of at least 580 M² /g.Surface area, as referred to herein, is determined by employing theLangmuir method of correlating adsorption/desorption isotherm data. TheLangmuir method is especially suitable for catalytic compositescontaining high percentages of crystalline aluminosilicates. The dataneeded for the Langmuir method is typically obtained by well knownadsorption/desorption apparatuses, preferably a nitrogenadsorption/desorption apparatus. Therefore, the present invention allowsfor a catalyst composition using a high surface area mordenite withoutloss of this surface area when formed with alumina to give acommercially acceptable formulation. Likewise, the benefit of thepresence of alumina, which imparts, among other things, strength to thecatalyst composition, may be achieved without penalty with regard to thesurface area of the mordenite.

Any method may be employed which results in a final catalyst compositehaving at least a surface area of 580 m² /g. Catalyst compositions withhigh surface areas can be arrived at in a number of ways, such as, usinga hydrogen form mordenite powder which inherently has a very highsurface area, or by having one component of the composite, which has ahigh surface area, in great proportion to other components. A preferredmethod of achieving a surface area of at least 580 m² /g is to contactthe formed catalytic composite with an acidic aqueous solution. Thisacidic aqueous solution may contain ammonium ions. The formed catalystcomposite may be dried and/or calcined prior to its contact with theaqueous solution.

The acidic nature of the aqueous solution is attained by employing anacid. Particularly suitable are strong mineral acids such as H₃ PO₄, H₂SO₄, HNO₃, and HCl. HCl is the preferred acid of the present invention.Of course, it is contemplated that mixtures of various acids may also beemployed. If the acidic aqueous solution contains ammonium ions, thepreferred source of these ions is NH₄ Cl, but any ammonium compoundwhich can form ammonium ions, such as NH₄ OH, NH₄ NO₃, NH₄ phosphatesand the like, should be suitable.

Concentrations of the acid and ammonium ions in the aqueous solution arenot critical and can vary from 0.5M to 6M for the acid concentration and0.5M to 4M for the ammonium ion concentration. Particularly good resultsare obtained using a solution containing acid and ammonium ionconcentrations within the range of 2 to 5M for the acid and 1 to 3M forthe ammonium ion.

A plurality of methods for contacting the formed catalytic composite andthe acidic aqueous solution is envisioned with no one method ofparticular advantage. Such contacting methods may include, for example,a stationary catalyst bed in a static solution, a stationary catalystbed in an agitated solution, a stationary catalyst bed in a continuouslyflowing solution, or any other means which efficiently contacts thecatalyst composition with the acidic aqueous solution.

The temperature of the contacting solution should be within the range of25° C. to about 100° C., preferably within the range of from about 50°C. to about 98° C. The time required for the contacting step will dependupon concentrations, temperature and contacting efficiency. In general,the contacting time should be at least 0.5 hour, but not more than 4hours, preferably between 1 and 3 hours in duration.

As a result of contacting the formed catalytic composite with the acidicaqueous solution, an increase in the measured surface area is observed.Surprisingly and unexpectedly, this increase in surface area, to 580 m²/g or higher, is not accompanied by an increase in the silica to aluminaratio of the hydrogen form crystalline aluminosilicate as measured byMagic Angle Spinning NMR (MASNMR). The MASNMR technique, which is a wellknown analytical method of the art, indicates no reduction in theframework tetrahedral aluminum atoms of catalyst compositions of thepresent invention. Although it is not certain the exact reason why thesurface area is higher after contacting the formed catalytic composite,it is believed that the acidic aqueous solution is removing occludedions from the mordenite which are deposited therein as a result of theforming technique employed.

The catalyst of the instant invention has particular utility in thealkylation or transalkylation of aromatic hydrocarbons.

In the alkylation of an aromatic substrate with an alkylating agent in aprocess utilizing the catalyst composition of this invention, thealkylating agent which may be charged to the alkylation reaction zonemay be selected from a group of diverse materials including monoolefins,diolefins, polyolefins, acetylenic hydrocarbons, and also alkylhalides,alcohols, ethers esters, the later including the alkylsulfates,alkylphosphates and various esters of carboxylic acids. The preferredolefin-acting compounds are olefinic hydrocarbons which comprisemonoolefins containing one double bond per molecule. Monoolefins whichmay be utilized as olefin-acting compounds in the process of the presentinvention are either normally gaseous or normally liquid and includeethylene, propylene, 1-butene, 2-butene, isobutylene, and the highmolecular weight normally liquid olefins such as the various pentenes,hexenes, heptenes, octenes, and mixtures thereof, and still highermolecular weight liquid olefins, the latter including various olefinpolymers having from about 9 to about 18 carbon atoms per moleculeincluding propylene trimer, propylene tetramer, propylene pentamer, etc.C₉ ≧C₁₈ normal olefins may be used as may cycloolefins such ascyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, etc.may also be utilized, although not necessarily with equivalent results.

It is a preferred embodiment of the present invention that themonoolefin contains at least 2 and not more than 14 carbon atoms. Morespecifically, it is preferred that the monoolefin is propylene.

The aromatic substrate component of the alkylation process of thisinvention which is charged to the alkylation reaction zone in admixturewith the alkylating agent may be selected from a group of aromaticcompounds which include individually and in admixture with benzene andmonocyclic alkylsubstituted benzene having the structure: ##STR1## whereR is a hydrocarbon containing 1 to 14 carbon atoms, and n is an integerfrom 1 to 5. In other words, the aromatic substrate portion of thefeedstock may be benzene, benzene containing from 1 to 5 methyl and/orethyl group substituents, and mixtures thereof. Non-limiting examples ofsuch feedstock compounds include benzene, toluene, xylene, ethylbenzene,mesitylene (1,3,5-trimethylbenzene), cumene, n-propylbenzene,butylbenzene, dodecylbenzene, tetradecylbenzene, and mixtures thereof.It is specifically preferred that the aromatic substrate is benzene.

In a continuous process for alkylating aromatic hydrocarbons witholefins, the previously described reactants are continuously fed into apressure vessel containing the above-described catalyst. The feedadmixture may be introduced into the alkylation reactions zonecontaining the alkylation catalyst at a constant rate, or alternatively,at a variable rate. Normally, the aromatic substrate and olefinicalkylating agent are contacted at a molar ratio of from about 1:1 to20:1 and preferably from about 2:1 to 8:1. The preferred molar feedratios help to maximize the catalyst life cycle by minimizing thedeactivation of the catalyst by coke and heavy material deposition uponthe catalyst. The catalyst may be contained in one bed within a reactorvessel or divided up among a plurality of beds within a reactor. Thealkylation reaction system may contain one or more reaction vessels inseries. The feed to the reaction zone can flow vertically upwards, ordownwards through the catalyst bed in a typical plug flow reactor, orhorizontally across the catalyst bed in a radial flow type reactor.

Temperatures which are suitable for use in the alkylation process hereinare those temperatures which initiate a reaction between an aromaticsubstrate and the particular olefin used to selectively produce thedesired product. Generally, temperatures suitable for use are from about100° to about 390° C., especially from about 150° to about 275° C.Pressures which are suitable for use herein preferably are above about 1atmosphere but should not be in excess of about 130 atmospheres. Anespecially desirable pressure range is from about 10 to about 40atmospheres; with a liquid hourly space velocity (LHSV) based upon thearomatic substrate feed rate of from about 0.5 to about 50 hr⁻¹, andespecially from about 2 to about 10 hr⁻¹. It should be noted that thetemperature and pressure combination used herein is to be such that thealkylation reaction takes place in essentially the liquid phase. In aliquid phase process for producing alkylated aromatics, the catalyst iscontinuously washed with reactants, thus preventing buildup of cokeprecursors on the catalyst. This results in reduced amounts of carbonforming on said catalyst in which case catalyst cycle life is extendedas compared to a gas phase alkylation process in which coke formationand catalyst deactivation is a major problem. To further reduce the rateof catalyst deactivation, it is contemplated that H₂ may be added to thealkylation reaction zone fed in an amount sufficient to saturate therespective reaction zone liquid feed. The addition of H₂ in equilibriumamounts to the respective liquid phase feed streams helps to reduce thecatalyst deactivation rate by inhibiting the polymerization potential ofpore blocking polymerizable compounds produced by the process.

The products of the alkylation reaction or transalkylation reaction ashereinbelow described may be recovered using techniques known in theprior art. Examples of some of the separation techniques that could beemployed alone or in combination to recover alkylation reaction zoneproducts are: distillation including vacuum, atmospheric, andsuperatmospheric distillation; extraction techniques including, forexample, liquid/liquid extractions, vapor/liquid extractions,supercritical extractions and others; absorption techniques, adsorptiontechniques, and any other known mass transfer techniques which canachieve the recovery of the desired separation zone products inessentially pure fractions. The separation processes mentioned above areincluded as examples of the many techniques which could be utilized toachieve the necessary separation, purification, and recovery of thealkylation reaction zone products. Hence, separation zone processingconditions are not disclosed as they will depend upon the choice of theseparation techniques employed and further upon the reactants used andthe configuration of the separation zone equipment. It is expected thatcontinuous distillation will be the primary separation technique used.The optimal distillation conditions will again depend upon the exactscheme chosen to achieve the desired separation.

The catalyst of this invention is also useful in the transalkylation oftransalkylatable aromatics. The transalkylation process of thisinvention preferably accepts as feed a transalkylatable hydrocarbon inconjunction with an aromatic substrate. The transalkylatablehydrocarbons useful in the transalkylation process are comprised ofaromatic compounds which are characterized as constituting an aromaticsubstrate based molecule with one or more alkylating agent compoundstaking the place of one or more hydrogen atoms around the aromaticsubstrate ring structure. The alkylating agent compounds identifiedabove are identical to those described as useful in the alkylationprocess above and preferably C₂ -C₁₄ aliphatic hydrocarbons.

The aromatic substrate useful as a portion of the feed to thetransalkylation process is the same as that described above as useful inthe alkylation process employing the instant catalyst.

The transalkylation process of this invention may have a number ofpurposes. In one, the catalyst of the transalkylation reaction zone isutilized to remove the alkylating agent compounds in excess of one fromthe ring structure of polyalkylated aromatic compounds and to transferthe alkylating agent compound to an aromatic substrate molecule that hasnot been previously alkylated, thus increasing the amount of the desiredaromatic compounds produced by the process. In a related purpose, thereaction performed in the transalkylation reaction zone involves theremoval of all alkylating agent components from a substituted aromaticcompound and in doing so, converting the aromatic substrate intobenzene.

To transalkylate polyalkylaromatics with an aromatic substrate, a feedmixture containing an aromatic substrate and polyalkylated aromaticcompounds in mole ratios ranging from 1:1 to 50:1 and preferably from4:1 to 10:1 are continuously or intermittently introduced into atransalkylation reaction zone containing the catalyst of this inventionat transalkylation conditions including a temperature from about 100° toabout 390° C., and especially from about 125° to about 275° C. Pressureswhich are suitable for use herein preferably are above 1 atmosphere butshould not be in excess of about 130 atmospheres. An especiallydesirable pressure range is from about 10 to about 40 atmospheres. Aliquid hourly space velocity (LHSV) of from about 0.1 to about 50 hr⁻¹,and especially from about 0.5 to about 5 hr⁻¹ based upon the combinedaromatic substrate and polyalkylaromatic feed rate is desirable. Whilethe process of the instant invention may be performed in the vaporphase, it should be noted that the temperature and pressure combinationutilized in the transalkylation reaction zone is preferred to be suchthat the transalkylation reactions take place in essentially the liquidphase. In a liquid phase transalkylation process for producingmonoalkylaromatics, the catalyst is continuously washed with reactants,thus preventing buildup of coke precursors on the catalyst. This resultsin reduced amounts of carbon forming on said catalyst in which casecatalyst cycle life is extended as compared to a gas phasetransalkylation process in which coke formation and catalystdeactivation is a major problem. Additionally, the selectivity tomonoalkylaromatic production, especially cumene production, is higher inthe catalytic liquid phase transalkylation reaction herein as comparedto catalytic gas phase transalkylation reaction.

The following examples are presented for purposes of illustration onlyand are not intended to limit the scope of the present invention.

EXAMPLES

A number of experiments were conducted to study how changes in thesurface area of alkylation or transalkylation catalyst composites affectprocess performance. Three catalysts were prepared for evaluation. Inall the catalyst preparations described in the following examples, thestarting material was the hydrogen form, low sodium, partiallydealuminated synthetic mordenite powder (marketed by Union Carbide underthe name LZ-M-8), hereinafter referred to as the as-received mordenite.

EXAMPLE I:

Experiments were undertaken to study the performance of two catalyticcomposites in promoting alkylation and transalkylation reactions.

Catalyst A was formulated by a method inconsistent with that of thealkylation or transalkylation catalyst of the present invention. Theas-received mordenite powder was mixed with an alumina powder to aweight ratio of 9:1, followed by the addition of an acidifiedpeptization solution. The admixture was then extruded by means known inthe art. After the extrusion process, the extrudate was dried andcalcined. The resulting surface area of this catalyst was 540 m² /g.

EXAMPLE II:

The catalyst base formulation used for Catalyst B is identical to thatused for Catalyst A of Example I. The difference arises in the stepsfollowing the drying and calcination of the acid peptizedsilica/mordenite extrudate. Following the drying and calcination steps,the extrudate was exposed to an aqueous solution comprising 10 wt. % HCland 10 wt. % NH₄ Cl at 60° C. for 150 minutes at a solution to zeolitevolumetric ratio of 5:1. After the acid wash step, the catalyst wasagain dried and calcined. Catalyst B is the acid-washed catalyst of thepresent invention. The resulting surface area of this catalyst was 620m² /g.

EXAMPLE III:

Catalyst C was formulated by a method inconsistent with that of thecatalyst of the present invention. To prepare Catalyst C, a mixture of50 wt. % mordenite powder and 50 wt. % alumina powder was combined witha 5.5 wt. % nitric acid solution. The resulting dough was extruded bymeans known in the art. The extrudate was calcined at 150° C. for 1 hourand then at 480° C. for 3 hours. The calcined extrudate was nextcontacted with a 15 wt. % solution of ammonia for 1 hour and then dried.The dried, finished extrudate was calcined at 150° C. for 1 hour and480° C. for 2 hours. The finished catalyst had a surface area of 450 m²/g.

EXAMPLE IV:

Catalysts B and C as described in the previous examples were evaluatedfor aromatic alkylation performance in a flow-through reactor containing20 cc of catalyst by processing a feed comprising a mixture of benzeneand propylene at a 4:1 molar ratio. Conventional product recovery andanalysis techniques were used to evaluate the catalyst performance ineach case.

The operating conditions used to evaluate the alkylation performance ofthe three catalysts comprised a reactor pressure of 34 atmospheres, aliquid hourly space velocity of 4 hr⁻¹ based upon the benzene feed rate,and a maximum temperature of 200° C. No recycle of the reactor effluentto the reactor inlet was employed in this testing. The results of thepilot plant tests can be found in Table 1 below.

                  TABLE 1                                                         ______________________________________                                                     Alkylation Reaction Selectivities                                               Catalyst B  Catalyst C                                         Yields (mole %)                                                                              200° C.                                                                            200° C.                                     ______________________________________                                        Cumene         85.9        82.6                                               Diisopropylbenzenes                                                                          12.2        16.1                                               para           4.4         5.9                                                meta           7.7         10.2                                               ortho          0.1         --                                                 ______________________________________                                    

The pilot plant tests indicate that Catalyst B, the alkylation catalystof the present invention produces an alkylation product which comprises98.1 mole % isopropylbenzene compounds of which 85.9 wt. % is themonoalkylaromatic cumene. Catalyst C, the low mordenite/low surface areacatalyst of the prior art produces an alkylate with 82.6 mole % of themonoalkylaromatic cumene. The only difference in preparation of the twocatalysts was that Catalyst B of the instant invention was treated withacid after forming which resulted in an increase in the surface area ofthe catalyst.

Thus, it can be concluded that the catalyst of the instant invention ismore useful in the production of monoalkylaromatics in an aromaticalkylation process directed toward the production of such products thanthe non-acid washed catalyst of the prior art.

EXAMPLE V:

Catalyst B, the transalkylation catalyst of the present invention, wastested at transalkylation reaction conditions along with Catalyst A, anon-acid washed mordenite catalyst, and Catalyst C, a low surface areamordenite catalyst, both not catalysts of the present invention. Thecatalysts were evaluated in a pilot plant consisting of a tubularreactor holding 50 cc of transalkylation catalyst and a product recoveryzone. To the reactor was fed a liquid feed blend comprised of 7.2 molesof benzene, 1 mole of diisopropylbenzene, and 0.25 moles of otheralkylbenzenes at a total liquid hourly space velocity (LHSV) of 1.3hr⁻¹. The reactor pressure was operated at 34 atmospheres, and thereaction temperature was held at 150° C. maximum. The results of thepilot plant tests are presented in FIGS. 1 and 2. It is evident fromFIG. 1 that the diisopropylbenzene conversion capability of Catalyst B,the transalkylation catalyst of the instant invention, is much higherthan that of the two catalysts not of the instant invention. The abilityof all three catalysts to promote the reaction of benzene withpolyalkylated aromatics as seen in FIG. 2 is similar in all cases. Thisleads to the conclusion that Catalyst B, the acid-washed high surfacearea transalkylation catalyst of the instant invention, is moreefficient in the transalkylation of diisopropylbenzene with benzene toproduce cumene at a high diisopropylbenzene conversion that a non-acidwashed or low surface area mordenite containing catalyst. This isevidenced as mentioned by the ability of Catalyst B to utilize an amountof benzene similar to Catalysts A and C to produce a greater amount ofisopropyl benzenes.

What is claimed is:
 1. A process for the transalkylation oftransalkylatable aromatics which comprises passing a feed streamcomprising a transalkylatable aromatic and an aromatic substrate into atransalkylation reaction zone containing a transalkylation catalyst, attransalkylation reaction conditions and recovering the transalkylationreaction zone products where the transalkylation catalyst comprises ahydrogen form mordenite dispersed in an alumina matrix, said compositecomprising from about 5 to 25 percent by weight of alumina, and whereinthe support is contacted with an acidic aqueous solution after it isformed, said contacting occurring at conditions selected to increase thesurface area of the composite to at least 580 m² /g without increasingthe silica to alumina ratio of the mordenite.
 2. The process of claim 1further characterized in that the transalkylation catalyst is spherical,cylindrical, or granular in shape.
 3. The process of claim 1 furthercharacterized in that the alumina is selected from the group consistingof gamma-alumina, eta-alumina, and mixtures thereof.
 4. The process ofclaim 1 further characterized in that the transalkylatable aromatic isselected from the group comprising a benzene substrate with from 1 to 6C₂ -C₁₄ alkyl groups attached thereto and mixtures thereof.
 5. Theprocess of claim 1 further characterized in that the aromatic substratefeed is benzene.
 6. The process of claim 1 further characterized in thatthe transalkylation reaction conditions comprise a temperature of from100°-390° C., a pressure of from 1 to 130 atmospheres, a liquid hourlyspace velocity of from 0.1 to 50 hr⁻¹, and an aromatic substrate totransalkylatable aromatic molar feed ratio of from 1:1 to 1:20.